A QUANTITATIVE-ANALYSIS OF A PREDICTIVE MODEL OF AMBULATORY BLOOD-PRESSURE MONITORING INTEGRATING PHYSICAL-ACTIVITY RECORDING

Objective : To determine how much of the variations of blood pressure during a 24 hour period could be accounted for by a change in activity using an accelerometer to detect the physical activity and establish a predictive model. Materials and methods : 18 healthy subjects (mean age 25 +/- 2 yrs) were studied during daily life (24 hours) twice one week apart. The systolic and diastolic blood pressure, heart rate (HR) , and time of measure were recorded by ambulatory monitoring using Spa celabs (4 mesures per hour). A portable digital memory device was desi gned for the 24 hours ambulatory monitoring of HR (ECG) and physical a ctivity. This device consists of an ECG Hotter (ELA medical model Cine sis with digital memory) and a three piezoresistive type accelerometer sensors (prototype ELA research) able to record physical activity in the 3 space dimension. Results : The data of the first recording were compared to the predicated values from the application of a logarithmi c model of activity to the second recording. The model then predicted 53 +/- 19 % of the systolic BP values of the test day. The mean indivi dual difference for a given time period of one hour between the measur ed and the predicted systolic BP from the model was 1.45 +/- 3.1 mmHg with a range of [-6.9; 3,4 mmHg]. The mean individual systolic BP diff erence for the same given time period of one hour but without predicti ve model was 1.29 +/- 10 mmHg with a range of [-28; 43 mmHg]. Conclusi on : This study show that 3 D accelerometer is an easy tool to program individual model of ambulatory blood pressure variability. The introd uction of this qualitative method seems logical in therapeutic trial.